dreams

Fantasies, usually visual, experienced during sleep
and in certain other situations. About 25% of an adult's sleeping time is
characterized by rapid eye movements
(REM) and brain waves that, registered on an electroencephalograph,
resemble those of a person awake (EEG). This REM-EEG state occurs in a number
of short periods during sleep, each lasting a number of minutes, the first
coming some 90 minutes after sleep starts an the remainder occurring at
intervals of roughly 90 minutes. It would appear that it is during these
periods that dreams take place, since people woken during a REM-EEG period
will report and recall visual dreams in 80% of cases; people woken at other
times report dreams only about 40% of the time, and of far less visual vividness.
Observation of similar states in animals suggests that at least all mammals
experience dreams. Dreams can also occur, though in a limited way, while
falling asleep (hypnogogic) or waking (hypnopompic); the origin of these
is not known.

Dream interpretation seems as old
as recorded history. Until the mid-19th century dreams were regarded as
supernatural, often prophetic; their possible prophetic nature has been
examined in this century by, among others J. W. Dunne. According to Sigmund
Freud, dreams have a latent content (the fulfillment of an individual's
particular unconscious wish) which is converted by dreamwork into
manifest content (the dream as experienced). In these terms, interpretation
reverses the dreamwork process.